Mechanical control of nanomaterials and nanosystems

Development and application of multiple-probe scanning probe microscopes

In the research of advanced materials based on nanoscience and nanotechnology, it is often desirable to measure nanoscale local electrical conductivity at a designated position of a given sample. For this purpose, multiple-probe scanning probe microscopes (MP-SPMs), in which two, three or four scanning tunneling microscope (STM) or atomic force microscope (AFM) probes are operated independently, have been developed. Each probe in an MP-SPM is used not only for observing high-resolution STM or AFM images but also for forming an electrical contact enabling nanoscale local electrical conductivity measurement. The world's first double-probe STM (DP-STM) developed by the authors, which was subsequently modified to a triple-probe STM (TP-STM), has been used to measure the conductivities of one-dimensional metal nanowires and carbon nanotubes and also two-dimensional molecular films. A quadruple-probe STM (QP-STM) has also been developed and used to measure the conductivity of two-dimensional molecular films without the ambiguity of contact resistance between the probe and sample. Moreover, a quadruple-probe AFM (QP-AFM) with four conductive tuning-fork-type self-detection force sensing probes has been developed to measure the conductivity of a nanostructure on an insulating substrate. A general-purpose computer software to control four probes at the same time has also been developed and used in the operation of the QP-AFM. These developments and applications of MP-SPMs are reviewed in this paper.

Recent advances in organic mechanofluorochromic materials

Mechanofluorochromic materials, which are dependent on changes in physical molecular packing modes, have attracted considerable interest over the past ten years. In this review, recent progress in the area of pure organic mechanofluorochromism is summarized, and majority of the reported organic mechanofluorochromic systems are discussed, along with their derived structure-property relationships. The existence of a structural relationship between aggregation-induced emission compounds and mechanofluorochromism is recognized based on our recent results, which considered aggregation-induced emission compounds as a well of mechanofluorochromic materials. The established structure-property relationship will guide researchers in identifying and synthesizing more mechanofluorochromic materials.

Ag Nanoparticle-Poly(acrylic acid) Composite Film with Dynamic Plasmonic Properties

Poly(acrylic acid) (PAA) thin films with embedded Ag nanoparticles (AgNPs) prepared by UV photoreduction exhibited cyclically changeable optical absorbance properties during variation of ambient aqueous medium. The observed phenomenon is due to conformational changes in the polymer matrix which leads to variation in the 3D configuration of the AgNPs ensemble. Reversible variation of the distance between nanoparticles during swelling and shrinking processes within the PAA matrix changes the optical parameters of these plasmonic metamaterials and can be considered a useful feature for optoelectronic devices and sensors. The finite-difference time-domain method was used for modelling of light extinction of developed matrix structures in their swollen and shrunken states.